1. Field of the Invention
The present invention is related to an electromagnetic reciprocating pump, and particularly to an electromagnetic reciprocating pump which enables the piston drive section to be cooled with a simple structure and can be manufactured at a low cost.
In addition, the present invention is related to an electromagnetic reciprocating pump wherein the piston drive section can effectively be cooled and the armature provided in the piston can be made lightweight.
2. Description of the Prior Art
The electromagnetic reciprocating pump is publicly known in which a fluid is repetitively sucked and discharged by displacing a piston having a piston head slidably disposed in a cylinder in one direction by means of a spring, and periodically attracting the piston in the direction opposite to the above-mentioned direction by means of an electromagnet, which is disposed in a casing so that a plurality of magnetic poles are positioned outside of the armature provided in the piston, thereby to reciprocating the piston. In the prior art electromagnetic reciprocating pump, if the magnetic action between the magnetic poles of the electromagnet and the armature becomes unbalanced even in a very small amount, the armature is moved to a magnetic pole side where the magnetic action is stronger, so that the piston may be partially abraded or broken. As a countermeasure for that, it is known to make the axis of the piston match the center line of the corresponding plural magnetic poles. An example of it is disclosed plural magnetic poles. An example of it is disclosed in the Japanese Utility Model Publication No. 47437/1982, which is known as an invention providing a remarkable effect of axes alignment.
In accordance with the electromagnetic reciprocating pump disclosed in the aforementioned publication, the opening for introducing air is communicating with a pressure chamber with the shortest distance, and thus the frictional heat between the piston and the main shaft for the piston, the Joule heat and the heat due to iron loss in the electromagnetic circuit or the like are not fully dissipated. Even if a port for introducing the cooling air is provided in the rear part of the casing, the cooling effect of the introduced air in the casing is not sufficient because of the closed-type casing and the heat is confined within the casing, which causes a problem that the main shaft temperature increased and the reciprocating motion becomes uneven because of thermal expansion or distortion.
It is also disclosed in the Japanese publication that, when the piston is supported on the main shaft, a sliding bearing of a small coefficient is fitted over the main shaft to expect a smooth reciprocating motion of the piston, but there is a problem that the life of the sliding bearing is adversely affected by such temperature increase of the main shaft as described above and shortened.
Further, there is a problem that, since the magnetic poles of the field core opposite to the armature are of only one pair, it is difficult to reduce the sectional area of the armature thereby for making the armature small size and lightweight.